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07/06/2017 – Ephemeris – Saturn will appear near the Moon tonight

July 6, 2017 1 comment

Ephemeris for Thursday, July 6th. Today the Sun will be up for 15 hours and 25 minutes, setting at 9:29, and it will rise tomorrow at 6:05. The Moon, 3 days before full, will set at 5:02 tomorrow morning.

The waxing gibbous Moon and the planet Saturn will appear together tonight. They are said to be in conjunction. The brightness of the Moon may make it hard to pick out Saturn which is right under the Moon by about seven Moon diameters. The Moon is very bright in binoculars or a telescope and looking at it destroys the dark adaption in the eye or eyes that look at it, at least for a while. So when viewing both Saturn and the Moon, concentrate of Saturn first. In a telescope Saturn’s rings are glorious. With a good telescope and enough magnification one might see the split in the rings, just inside the outer edge of them called Cassini’s Division, after it’s discoverer. The large moon Titan is off the western extremity of the rings tonight.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

 

Saturn and the Moon

The Moon and Saturn at 10:30 p.m., July 6, 2017, as it would be seen from northern Michigan. Created using Stellarium.

Saturn showing Cassini's Division

Saturn and its rings with Cassini’s Division. Created using Stellarium.

Ring particles at the distance of Cassini’s Division from Saturn orbit the planet twice in the time the satellite Mimas, nicknamed the Death Star, orbits the planet once.  Ring particles are thus tugged by Mimas’ gravity away from Saturn in the same place every other orbit, which pulls them out of that particular orbital resonance.

Mimas

“That’s no moon!” Yes it is. Saturn’s moon Mimas, It’s diameter is 123 miles (198 km). The huge crater is named Herschel, after the moon’s discoverer William Herschel. Credit: NASA / JPL-Caltech / Space Science Institute.

06/15/2017 – Ephemeris – Saturn is at opposition from the Sun today

June 15, 2017 1 comment

Ephemeris for Thursday, June 15th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, 2 days before last quarter, will rise at 1:28 tomorrow morning.

The Planet Saturn was in opposition with the Sun at 5:15 (09:15 UT) this morning. That means that it was 180 degrees from the Sun, well 178.6 degrees to be exact, because the Earth is a bit south of the Sun-Saturn line. This is a time when the shadows of the rings on the planet and planet on the rings almost disappear, due to our vantage point. Saturn is also closest now at 842 million miles (1.356 billion km). It average distance being about 940 million miles (1.5 billion km). In three months our emissary to Saturn, the Cassini spacecraft will dive beneath Saturn’s clouds to burn up after using up almost all its maneuvering fuel. Then we with our telescopes on and around Earth will remain the only link to the ringed planet.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Saturn at opposition

Saturn at opposition in a perspective view of the solar system which compresses the fact that Saturn is 10 times farther from the Sun as the Earth. Created using my LookingUp program.

06/12/2017 – Ephemeris – Now is a great time to view Saturn

June 12, 2017 Comments off

Ephemeris for Monday, June 12th. Today the Sun will be up for 15 hours and 31 minutes, setting at 9:28, and it will rise tomorrow at 5:56. The Moon, 3 days past full, will rise at 11:44 this evening.

In three days the planet Saturn will be opposite the Sun in the sky. Astronomers simply call it opposition. It’s the time Saturn will be closest to us, and appear biggest in telescopes. That’s not a big a deal as for a closer, smaller planet like Mars or Venus. Being ten times farther from the Sun than the Earth Saturn’s distance and thus it’s size varies by only plus or minus 10%. Another event happened on Saturn last month, Summer started in it’s northern hemisphere. Saturn’s rings orbit the planet over it’s equator, and Saturn’s axial tilt of obliquity is 26 degrees, similar to the Earth’s actually. This summer solstice means that the rings are at their most open because we are viewing Saturn from near the Sun, so a first glance through a telescope Saturn looks elliptical, with the planetary ball completely within the rings.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Saturn's Rings over time

Saturn’s Rings over time as they closed. Credit NASA/HST/WFPC2

Now the rings are opened to their maximum extent with the northern hemisphere of Saturn uncovered by the rings and the southern hemisphere covered by them, the reverse of the top image.

Categories: Ephemeris Program, Saturn

05/11/2017 – Ephemeris – Cassini is surviving its death-defying dives under the rings of Saturn

May 11, 2017 Comments off

Ephemeris for Thursday, May 11th.  Today the Sun will be up for 14 hours and 40 minutes, setting at 8:59, and it will rise tomorrow at 6:17.  The Moon, 1 day past full, will rise at 9:42 this evening.

The Cassini spacecraft has been redirected by passing Titan on a special trajectory that sent it into a fatal set of orbits that take it a few thousand miles above Saturn’s cloud tops and under the innermost rings.  So far after two passes Cassini survives.  One discovery of the first pass was a storm, perhaps a hurricane, whose clear eye is at Saturn’s north pole.  Cassini has yet to turn its cameras to the rings on these passes inside the rings, but it will before its final orbit.  Currently it is flying communication dish first to protect its delicate instruments from ring particles.  So far the gap between the rings and the planet are more free of particles than expected.  Which is a good omen for the last 20 passes between the rings and planet.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini's grand finale

In its planned last 22 orbits of Saturn, the Cassini spacecraft will pass between the innermost ring and the planet itself. Credit NASA, JPL.

Saturn's North Pole

The clearing (blue sky) in the clouds at Saturn’s north pole spotted by Cassini on its first pass under the rings. Credit: NASA/JPL-Cal Tech/S Si/Sophia Nasr

 

04/25/2017 – Ephemeris – The Cassini spacecraft is on its last 22 orbits of Saturn

April 25, 2017 2 comments

Ephemeris for Tuesday, April 25th.  The Sun rises at 6:41.  It’ll be up for 13 hours and 58 minutes, setting at 8:40.  The Moon, 1 day before new, will rise at 7:08 tomorrow morning.

In the early hours of last Saturday, Earth Day, The Cassini spacecraft, orbiting Saturn for the last nearly 13 years, made its last pass of Saturn’s giant moon Titan.  Over the past 13 years Cassini has been using Titan as a kind of fulcrum to leverage its orbits of Saturn, returning time and time again to both study this strange moon and to propel it via gravity assists into a myriad of orbits.  This time however, with one last gravitational assist, Cassini was flung into a series of 22 daring orbits which will take it into a couple of thousand mile gap between the rings and the planet.  On orbit 22, if it doesn’t collide with an errant ring particle, Cassini will burn up in Saturn’s atmosphere, going something like 70,000 miles an hour on September 15th.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Cassini's grand finale

In its planned last 22 orbits of Saturn, the Cassini spacecraft will pass between the innermost ring and the planet itself. Credit NASA, JPL.

02/21/2017 – Ephemeris – Finding Saturn this morning and Cassini’s future

February 21, 2017 Comments off

Ephemeris for Tuesday, February 21st.  The Sun will rise at 7:32.  It’ll be up for 10 hours and 47 minutes, setting at 6:19.  The Moon, 3 days past last quarter, will rise at 4:48 tomorrow morning.

This morning the crescent Moon will act as a pointer to the planet Saturn.  The ringed planet will appear to the right of our Moon.  Saturn’s rings will show in any telescope with 20 times magnification or greater.  Out at Saturn for the last 13 years and for the next 7 months the robot spacecraft Cassini has been orbiting the ringed planet using gravity assists from the giant moon Titan as a fulcrum to leverage itself into many different orbits to study Saturn’s rings and collection of moons.  In a bit over seven months it’s fantastic journey will be over.  Low on fuel, it will plunge between the rings and the cloud tops, spiraling in towards its doom September 30th into the planet’s atmosphere so as not to contaminate the icy moons which could possibly harbor life.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Finding Saturn

Using the Moon to locate Saturn in the southeast at 7 a.m. or earlier on February 21, 2017. The Moon is enlarged to show it better. Created using Stellarium.

Cassini Spacecraft

The Cassini spacecraft at Saturn. Credit: NASA/JPL.

Prometheus and the F Ring

The shepherd satellite Prometheus leaving a wake in Saturn’s outer F Ring. Credit: NASA/JPL.

01/24/2017 – Ephemeris – The Moon is near Saturn this morning

January 24, 2017 Comments off

Ephemeris for Tuesday, January 24th.  The Sun will rise at 8:09.  It’ll be up for 9 hours and 31 minutes, setting at 5:40.  The Moon, 3 days before new, will rise at 6:08 tomorrow morning.

This morning look low in the southeast to see the thin crescent Moon with the planet Saturn below and to the right.  The Moon passed Saturn a little after they rose.  Saturn is quite far south in our skies, almost as far south as the Sun was on the winter solstice on December 21st.  It will take a while to rise high enough in deep twilight or darkness for good views with a telescope.  When Saturn or any planet is low on the horizon we are looking at it through a lot of our atmosphere.  Beside draining about half its brightness that atmospheric motions make the planet fuzzy in telescopes.  Yes, you can still see the rings, but the gaps on each end between the rings and the planet may not be distinct, and its large moon Titan may not be visible at all.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The morning planets and the Moon at 7 a.m. this morning, January 24th.  Because planetarium programs don't show a thin crescent very well, I've enlarged the Moon by a factor of 4 times.  Created using Stellarium.

The morning planets and the Moon at 7 a.m. this morning, January 24th. Because planetarium programs don’t show a thin crescent very well, I’ve enlarged the Moon by a factor of 4 times to make the Moon show up at all.  Click on the image to enlarge. Created using Stellarium.